In a typical cellular radio access network (RAN), an area is divided geographically into a number of coverage areas (namely, cells and cell sectors) defined by radio frequency (RF) radiation patterns from base transceiver stations (BTSs). All of the BTSs in a region may then be communicatively linked with a common RAN controller that manages certain operations of the BTSs and that may function as an aggregation point for communications passing through the BTSs.
For instance, a cellular service provider's market may be divided into local regions each containing a number of BTSs that are communicatively linked with a common base station controller (BSC) that manages the BTSs and that functions as an aggregation point and RAN controller. Further, the BSCs of various local regions may then be coupled with a common switch or gateway, such as a mobile switching center (MSC) or packet data serving node (PDSN), that functions as a broader aggregation point and a broader RAN controller, and that may provide connectivity with a transport network such as the public switched telephone network (PSTN) or the Internet. Other examples are possible as well.
When a mobile station (such as a cellular telephone, pager, or appropriately equipped portable computer, for instance) is positioned in a coverage area of such a system, the mobile station communicates via an RF air interface with the BTS antennas that radiate to define the coverage area. Consequently, a communication path may be established between the mobile station and the transport network, via the air interface, the BTS, the BSC and the switch or gateway.
In practice, communications over the air interface between a BTS (base station) and a mobile station will comply with a defined air interface protocol or “access technology.” Numerous such protocols are well known in the art, and others will be developed in the future. Examples of existing protocols include CDMA (e.g., 1xRTT, 1xEV-DO), iDEN, TDMA, AMPS, GSM, GPRS, UMTS, EDGE, WiMAX (e.g., IEEE 802.16), LTE, microwave, satellite, MMDS, Wi-Fi (e.g., IEEE 802.11), and Bluetooth.
In general, when RAN controller (e.g., MSC and/or BSC) encounters a trigger event that indicates a need to transmit information to a given mobile station, RAN controller may cause multiple BTSs to page the mobile station. For instance, the RAN controller may initiate paging in the coverage area where the mobile station was last registered and in various coverage areas surrounding that coverage area, out to a particular radius defining a paging area. If the mobile station responds to the page, then the RAN controller would thereby learn the coverage area in which the mobile station is currently operating, and the RAN controller may arrange for transmission of the information to the mobile station in that coverage area.
In each wireless coverage area, the air interface defined by the serving BTS may be divided into various discrete channels by applying one or more mechanisms, such as unique spread-spectrum coding, time division multiplexing, and/or frequency differentiation, for instance. One or more of the channels in each coverage area may be reserved for use as a paging channel, on which the BTS may broadcast page messages destined to particular mobile stations. And one or more of the channels in each coverage area may be reserved for use as an access channel, on which mobile stations may transmit page response messages to the RAN. In practice, when a BTS receives from a RAN controller a directive to page a mobile station, the BTS may thus responsively broadcast on the paging channel a page message directed to that mobile station. If and when the mobile station receives the page message, the mobile station may then programmatically transmit a page response message to the RAN on the access channel.